1. Field of the Invention
The present invention relates to a chemical coating apparatus which has a chemical pipe through which a chemical flows, and a heat exchanger disposed along at least part of the chemical pipe and in which the temperature of the chemical is adjusted to a predetermined value by the heat exchanger.
2. Description of the Related Art
A chemical coating apparatus of this type is used in various forms. It is known, for example, as a resist coater which is used to apply a resist on the surface of a semiconductor wafer during the process of manufacturing semiconductor devices.
FIG. 1 shows the arrangement of such a known resist coater. With this apparatus, a semiconductor wafer 3 is attached by means of vacuum to a rotary chuck 2 disposed in a cup 1, a coating is applied by dropping resist liquid 5 onto the semiconductor wafer 3 while the wafer 3 is being rotated by the operation of a chuck rotating motor 4.
The resist liquid 5 applied to the semiconductor wafer 3 is supplied by a resist liquid supply device (not shown), and is then subjected to indirect exchange of heat in a heat exchanger 6 through which constant-temperature water 7 having an adjusted temperature circulates, thereby adjusting the temperature of the resist liquid 5. After the resist has had its temperature adjusted in this way, it flows through a chemical pipe 9, such as a Teflon tube, and is then discharged from a chemical nozzle 8 to coat the semiconductor wafer 3.
With the known resist coating apparatus, however, since the resist liquid 5 at the tip of the nozzle 8 is easily influenced by the peripheral temperature, the thickness of a resist film applied to the semiconductor wafer 3 tends to vary to a great extent. It is therefore difficult to control the thickness of the resist film, resulting in various problems. For instance, the film thickness may vary within the surface of a single semiconductor wafer, and it may also vary among a plurality of wafers.